AndroidTextView实现多文本折叠、展开效果

private void initData() {
 mTvMoreLineShort.setText(Constant.content1);
 mTvExpandableShort.setText(Constant.content2);
 mTvMoreLineLong.setText(Constant.content3);
 mTvExpandableLong.setText(Constant.content4);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 // 如果没有变化，测量并返回
 if (!mRelayout || getVisibility() == View.GONE) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  return;
 }
 mRelayout = false;

 super.onMeasure(widthMeasureSpec, heightMeasureSpec);

 // 内容区域初始显示行高
 mTvContent.setHeight(mTvContent.getLineHeight() * (mMaxLine > mTvContent.getLineCount() ? mTvContent.getLineCount() : mMaxLine));
 mLlExpand.post(new Runnable() {

  @Override
  public void run() {
   // 是否显示折叠效果
   mLlExpand.setVisibility(mTvContent.getLineCount() > mMaxLine ? View.VISIBLE : View.GONE);
  }
 });
}

/**
 * @Description 设置显示内容
 */
public void setText(String str) {
 mRelayout = true;
 mTvContent.setText(str);
 setVisibility(TextUtils.isEmpty(str) ? View.GONE : View.VISIBLE);
}

@Override
public void onClick(View v) {
 if (mTvContent.getLineCount() <= mMaxLine) {
  return;
 }
 isExpand = !isExpand;
 mTvContent.clearAnimation();
 final int deltaValue;
 final int startValue = mTvContent.getHeight();
 if (isExpand) {
  deltaValue = mTvContent.getLineHeight() * mTvContent.getLineCount() - startValue;//计算要展开高度
  RotateAnimation animation = new RotateAnimation(0, 180, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
  animation.setDuration(mDurationMillis);
  animation.setFillAfter(true);
  mIvExpand.startAnimation(animation);
  mTvExpand.setText(getContext().getString(R.string.collapse));
 } else {
  deltaValue = mTvContent.getLineHeight() * mMaxLine - startValue;//为负值，收缩的高度
  RotateAnimation animation = new RotateAnimation(180, 0, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
  animation.setDuration(mDurationMillis);
  animation.setFillAfter(true);
  mIvExpand.startAnimation(animation);
  mTvExpand.setText(getContext().getString(R.string.expand));
 }
 Animation animation = new Animation() {
  protected void applyTransformation(float interpolatedTime, Transformation t) {
   //interpolatedTime:为当前动画帧对应的相对时间，值总在0-1之间,原始长度+高度差*（从0到1的渐变）即表现为动画效果
   mTvContent.setHeight((int) (startValue + deltaValue * interpolatedTime));
  }
 };
 animation.setDuration(mDurationMillis);
 mTvContent.startAnimation(animation);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 // 如果没有变化，测量并返回
 if (!mRelayout || getVisibility() == View.GONE) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  return;
 }
 mRelayout = false;

 // Setup with optimistic case
 // i.e. Everything fits. No button needed
 mLlExpand.setVisibility(View.GONE);
 mTvContent.setMaxLines(Integer.MAX_VALUE);

 // Measure
 super.onMeasure(widthMeasureSpec, heightMeasureSpec);

 //如果内容真实行数小于等于最大行数，不处理
 if (mTvContent.getLineCount() <= mMaxCollapsedLines) {
  return;
 }
 // 获取内容tv真实高度（含padding）
 mTextHeightWithMaxLines = getRealTextViewHeight(mTvContent);

 // 如果是收起状态，重新设置最大行数
 if (mCollapsed) {
  mTvContent.setMaxLines(mMaxCollapsedLines);
 }
 mLlExpand.setVisibility(View.VISIBLE);

 // Re-measure with new setup
 super.onMeasure(widthMeasureSpec, heightMeasureSpec);

 if (mCollapsed) {
  // Gets the margin between the TextView's bottom and the ViewGroup's bottom
  mTvContent.post(new Runnable() {
   @Override
   public void run() {
    mMarginBetweenTxtAndBottom = getHeight() - mTvContent.getHeight();
   }
  });
  // 保存这个容器的测量高度
  mCollapsedHeight = getMeasuredHeight();
 }
}

/**
 * @Description 设置显示内容
 */
public void setText(CharSequence text) {
 mRelayout = true;
 mTvContent.setText(text);
 setVisibility(TextUtils.isEmpty(text) ? View.GONE : View.VISIBLE);
}

@Override
public void onClick(View view) {
 if (mLlExpand.getVisibility() != View.VISIBLE) {
  return;
 }

 mCollapsed = !mCollapsed;
 // 修改收起/展开图标、文字
 setDrawbleAndText();
 // 保存位置状态
 if (mCollapsedStatus != null) {
  mCollapsedStatus.put(mPosition, mCollapsed);
 }

 // 执行展开/收起动画
 mAnimating = true;
 ValueAnimator valueAnimator;
 if (mCollapsed) {
  valueAnimator = new ValueAnimator().ofInt(getHeight(), mCollapsedHeight);
 } else {
  mCollapsedHeight = getHeight();
  valueAnimator = new ValueAnimator().ofInt(getHeight(), getHeight() + mTextHeightWithMaxLines - mTvContent.getHeight());
 }

 valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {

  @Override
  public void onAnimationUpdate(ValueAnimator valueAnimator) {
   int animatedValue = (int) valueAnimator.getAnimatedValue();
   mTvContent.setMaxHeight(animatedValue - mMarginBetweenTxtAndBottom);
   getLayoutParams().height = animatedValue;
   requestLayout();
  }
 });

 valueAnimator.addListener(new Animator.AnimatorListener() {

  @Override
  public void onAnimationStart(Animator animator) {

  }

  @Override
  public void onAnimationEnd(Animator animator) {
   // 动画结束后发送结束的信号，清除动画标志
   mAnimating = false;
   // 通知监听
   if (mListener != null) {
    mListener.onExpandStateChanged(mTvContent, !mCollapsed);
   }
  }

  @Override
  public void onAnimationCancel(Animator animator) {

  }

  @Override
  public void onAnimationRepeat(Animator animator) {

  }
 });

 valueAnimator.setDuration(mAnimationDuration);
 valueAnimator.start();
}